In a WRX I bought new and sold with 136K on it, I put in Supertech semi synthetic 75W90 in the manual transmission early in it's life and stuck with that gear oil throughout me owning it. I chose it because it is a rare gear oil not intended to service limited slip differentials. You don't want the most slippery oil in a manual transmission. It provided me very good shift quality. It gets good reviews in the Subaru community.